1. Field of the Invention
The present invention relates to a vehicle control device and a vehicle control method for controlling a motion state of a vehicle, and particularly relates to a method of controlling the motion state of the vehicle by adjusting an element of a system matrix in a state equation that represents the motion state of the vehicle.
2. Description of the Related Art
There has been hitherto known a vehicle control method for controlling a motion state of a vehicle by controlling a driving/braking torque applied to a wheel or by controlling a suspension performance of the wheel. According to this vehicle control method, the motion state of the vehicle is controlled to be optimized, for instance, under a driving condition such as cornering, in order to enhance steering stability. Such technologies include a vehicle control device that controls the motion state of the vehicle with use of a wheel-frictional-force utility factor (see the JP-3132190, for example). This vehicle control device obtains the wheel-frictional-force utility factor for each wheel, and controls a wheel state of each wheel such that the wheel-frictional-force utility factor approaches a target wheel-frictional-force utility factor. The wheel-frictional-force utility factor is calculated as a percentage of an actual frictional force that is a resultant force of a longitudinal force and a lateral force that are actually being generated between a wheel and a road surface, to the maximum frictional force that is a product of an actual friction coefficient between the wheel and the road surface and a vertical force actually being generated between the wheel and the road surface.
In addition, the JP-A-11-102499 discloses a method of controlling a motion state of a vehicle by focusing on an element of a matrix in a state equation that represents the motion state of the vehicle, based on knowledge that the element affects characteristic of the vehicle.